I'm interested in marine desalinization. Most every device I have seen this far is some fossil-fuel driven high pressure pump.
- Are there electric ones?
- Is high pressure even that necessary to produce a reasonable amount of potable water?
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2High pressure is inherent to reverse osmosis systems, which account for most large-scale desalination. Electric pumps can easily active the pressures but there's often no electricity to spare on a boat, so you may need to look for a non-marine system if you want an electric system.– Chris HMay 14, 2016 at 7:52
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Perhaps you are looking for something like this. Unfortunately it doesn't seem to be in production yet. There are other solar-powered systems (e.g. this one) but I think most are rather big and expensive.– THelperMay 14, 2016 at 9:50
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3Power requirement for such devices greatly depends on the amount of water you want to produce, and also the technique used. Wikipedia describes various techniques and energy consumptions in KWh/m3: en.wikipedia.org/wiki/Desalination ; RO looks to be the best if you don't have a cheap heat source around.– J. ChomelMay 15, 2016 at 18:34
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1There are hand-pumped versions for small amounts of water, but they're hard work! Sometimes installed on yachts doing ocean crossings to give an emergency supply for a small crew.– FlytoMay 17, 2016 at 5:39
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2 Answers
Most every device I have seen this far is some fossil-fuel driven high pressure pump.
You need to look at more devices. We live on a sailboat and make our own water and every single boat (sail or power) I have ever been on, seen, or heard of that has a reverse osmosis watermaker has an electric one.
- Are there electric ones?
Definitely. Some run on AC some on DC. Ours is a PUR PowerSurvivor 160E. It runs on 12v and turns seawater into fresh at the rate of 6.7 gallons per hour. This particular unit runs at approximately 16 amps (but it does fluctuate because the pressure is constantly changing making the motor resistance more/less). Like most sailboats we have a 12v battery bank that is maintained by solar panels. No fossil fuels.
Most of the people I know with 120v AC watermakers usually run some sort of generator (or their aux engines) at the same time they are making water.
If you want truly "green" desalination, Katadyn is a reputable company and makes the smallest watermaker in the world, but it's hand operated. Look for the Katadyn Survivor 06.
- Is high pressure even that necessary to produce a reasonable amount of potable water?
Absolutely. It takes a large amount of energy to remove the salt and other minerals from sea water. From our user manual for the PUR:
"For every gallon of pure water made, up to 10 gallons of seawater must be pressurized.
So 90 percent of the energy used in conventional reverse osmosis is lost."
The high pressure hoses on our unit are no different than the high pressure hydraulic hoses you would see on a tractor. The motor is trying to push all that seawater through a membrane that only allows the smallest of particles to pass.
We are able to avoid expensive marinas by being able to make all of our own water and electricity. Do a search on watermakers and sailboats and you will find all the information you need on seawater desalination because sailors all over the world have and use these systems. There is tons of information about this out there.
At sea, distillation is often more preferred to reverse osmosis systems. Navies still use this Method for production of water because it's efficient, it often uses the ships waste heat from it's engines to flash boil water.
